Electric discharge device and method of fabrication thereof



y 9 4.- I J. r-:.- BEGGSV 2,352,933

ELECTRIC DISCHARGE DEVICE-MID METHOD'OF FABRICATION THEREOF Filed on;29. 1942 2 VShe etS-Shaat 1 Inventor: James B. Beggs,

Joy

His Attorney July 4,

.1. E. 85665 2,352,933 ELECTRIC DISCHARGE DEVICE AND METHOD OFFABRICATION THEREOF Filed Oct. 29, 1942 2 Sheets-Sheet 2 Inventor; JamesE 'Beggs, b l/ myifl y HIS/Attorney Patented July 4, 1944 ELECTRICDISCHARGE DEVICE AND METHOD or FABRICATION THERE- James E. Beggs,Scotia, N. Y., assignor to General Electric Company, a corporation ofNew York Application October 29, 1942. Serial No. 463,784

19 Claims.

My invention relates to electric discharge devices and more particularlyto new and improved electric discharge devices and a method offabrication thereof.

In the construction of electric discharge devices there has been an everpresent need for improvements which facilitate the arrangement andassembly of the parts thereof. In accordance with the teachings of myinvention described hereinafter, I provide new and improved electricdischarge devices and a method of manufacture or fabrication thereofwhich afford advantages not incident to the prior art arrangements.

It is an object'of my invention to provide new and improved electricdischarge devices. It is another object of my invention to provide newand improved construction of electric discharge devices applicable todevices of the high vacuum type, or the type employing an ionizablemedium such as a gas or a vapor.

It is still another object of my invention to provide a new and improvedmethod of construction and assembly of electric discharge devices.

It is a still further object of my invention to provide a new andimproved construction of electric discharge devices whereby all or amajority of the essential elements and control elements ductors forelectrode members, whereby the connections between the electrodes andthe supporting conductors may be made in a position which is readilyaccessible in the manufacturing operation.

Briefly stated, in the illustrated embodiments of my invention I providea new and improved construction for electric discharge devices, and anew and improved method of assembly of the various elements or partsthereof. More particularly, I provide a header supporting a plurality ofspaced vertical conductors sealed to the header and which are adapted tobe threaded through openings in a pair of horizontal verti-Cally-disposed insulating spacers. All or a maor required, I provideelectrostatic shielding means preferably located above the topinsulating spacer and which serves to shield the control elements fromthe anode.

For a better understanding of my invention, reference may be had to thefollowing description, taken in connection'with the accompanyingdrawings, and its scope will be pointed out in'the appended claims. Fig.l fof the drawings diagrammatically illustrates an assembled view of anelectric discharge device'built in accordance with my invention, andFigs. 2 -6, inclusive, represent certain detailed views of essentialaspects of the device shown in Fig. 1. Fig. '7 diagrammaticallyrepresents the electrode assembly and the header construction in onestep of the assemblyor manufacture of the device. Figs. 841, inclusive,represent a modification of my invention as applied to a pentodeconstruction.

' Referring now to Fig. 1 of the accompanying drawings, I have thereillustrated my invention as applied to an electric discharge device ofthe type comprising a plurality of electrodes enclosed within anenvelope l which maybe constructed of a suitable metal such as iron, andwhich is seated onand sealed to a metallic header 2, theopen end of theenvelope I being positioned in a trough of" annular groove 3." Theenvelope 1 may be soldered to the header 2. The operation of evacuationor gas-filling may be obtained by the conventional bell-jar arrangementby dropping the envelope I into the position illustrated when thedesired atmospheric condition is produced, thereby forming ahermetically sealed enclosure for the electrodes of the device. Asuitable solder. 4

a maybe positioned'in the annular groove 3 to jority of the electrodesof the discharge device the elements of the discharge device is desiredtion.

form a continuous seal between theen've1ope l and the header2. f I

The details of the header construction may be more fully appreciated byreferring to Fig. 2 wherein the metallic header is shown. Theheader 2may be'constructed of iron and formed by a stamping operation to producethe desired configuration. 'A'plurality' of protuberances 5 .may beformed inthe header 2 by an extrusion opera- "tion and'se'rve as a meansfor positioning a plurality of spaced'vertical supporting members orconductors 6-13, inclusivej Conductors,6--"I 3are sealed to theheader'2Ib-y suitable glass to metal seals i l positionedbetween thevarious conductors'and the extruded portionsof the header 2. Whereconductors 6-43 are constructed of iron, the glass-to-metal'seal may beof the type disclosed and claimed in U. S. Letters Patent No.2,272,747,'granted February 10, 1942 upon an ape plication of Albert'W.Hull et al, andwhich is assigned to "the assignee' of the presentapplica- In "one embodiment of my invention, the anode comprises asubstantially plane 'surfa'ce formed by a metal plate l5vvhicli maybe'welded to one of the vertical conductors, such as conductor 6.

The ends of conductors 6-l3, inclusive, which extend below the header 2,may be supported by an insulating base It constructed of a resinous orother suitable material. These conductors may be terminated in andwelded or soldered to a plurality of pin contacts which are secured tothe base iii. For example, conductors 6-), inclusive, may be terminatedin contact pins I1-2 l, inclusive, which are secured to base I6. Header2 and base l6 may be maintained in the position illustrated by providingskirt 22 of header 2 with sufficient resilience and configuration tohold the members rigidly in position, or the skirt 22 may be providedwith crimped locks (not shown) which engage base l6 at spaced points.

I provide an electrode assembly which facilitates the fabrication ormanufacture of an electric discharge device and which comprises a pairof substantially parallel spaced or vertically-disposed insulatingspacers 23 and 24 which may serve as a support for all or a majority ofthe electrodes of the discharge device, and which may be assembled as aunit prior to positioning upon the header construction. One of theinsulating spacers, such as the bottom insulating spacer 24, is shown indetail in Fig. 3. It will be noted that the insulating spacer 24 isprovided with a plurality of openings 25-32, inclusive, displaced fromthe periphery of the spacer, and through which conductors '6-l3,inclusive, are threaded. It will be observed that opening 25 has aconfiguration suitable to permit the passage not only of conductor 6therethrough but also of plate member 15. In addition, it will be notedthat openings 33 and 34 are provided to permit the insertion of theextremities of a cathode and control element therethrough. In thismanner, by the proper dimensioning of openings 33 and 34 relative to thesize 'of cathode and control element, the spacer 24 acts as a lowersupport for the cathode and control element. Insulating spacer 24 isalso provided with openings 33-33, inclusive, which receive fasteningmembers comprising part of a rigid electrode construction, such as ascreen grid or an anode to be described hereinafter.

In one modification of my invention, the insulating spacers 23 and 24may be held rigidly in position, thereby effecting a rigid constructionfor the support of other elements of the discharge device, by employinga wall-like element such as a screen grid 39 shown in detail in Fig. 4.The screen grid 39 may be formed to be a substantially continuousmetallic member provided with a plurality of pliable metallic pendantsor tabs 40 at both the top and'the bottom. The bottom tabs are insertedinto openings 35-38 of the insulating spacer 24 and may be turned orbent over on the under surface, thereby securing the electrode 39 firmlyagainst the surface of the spacer 24.

The details of the configuration of the screen grid construction 39 maybe more fully appreciated by referring to Fig. 6. It will be noted thatthe screen grid 39 is provided with a transverse metallic partition "4|having therein an opening 42 to provide a communicating path between avertically disposed thermionic cathode 43 and the anode member I5. Thelower extremity of the thermionic cathode 43 may be maintained in andsupported by openings 33 of the lower insulating spacer 24. In likemanner, a control element or grid 44 may be maintained in a verticalposition by having one extremity extending into the opening 34 of thelower spacer 24. Of course, it will be appreciated that the upperextremities of cathode 43 and control element 44 also extend intosuitable openings of the top insulating spacer 23, so that theseelements are maintained in the desired spaced relation with respect toeach other as well as to the other elements of the discharge device.

Fig. 5 represents a top view of the electrode assembly and theconnections between the various elements thereof and the vertical orupright conductors. One advantage of employing this type of constructionis that the connections to all of the elements thereof may be made at apoint readily accessible, that is in the top position or the regionlying directly above the top insulating spacer 23. An additionaladvantage is the ease with which the insulating spacer 23 is secured inposition. For example, the conductor I3, which in the tetrodeconstruction illustrated is not needed for an electrical connection, maybe bent over and pressed against the top surface of the spacer 23,thereby acting as an additional securing member.

Cathode 43 may be connected to the vertical conductor 9 by means of aconductor means or connection 45 which is welded or soldered at itsextremities to the cathode and conductor 9, re-

spectively. Cathode 43 may be of the indirectly heated type comprising awound heating coil 46 within the cylindrical construction, and theoathode heating terminals or conductors 4'! and 48 are electricallyconnected to vertical conductors l0 and '1, respectively. In order toeffect a rigid construction to prevent undesired flexing of theconnection, a rigid conductor 49 may extend from terminal 48 toconductor 1. It will be noted that the upper extremities of the verticalconductors above the surface of top insulating spacer 23 may be bentover to act as additional means for securing the spacer in place and tofacilitate welding or soldering the various connections to theconductors.

Where it is desired to employ a directly heated gettering material, sucha gettering material may be connected between one of the verticalconductors, such as conductor 9, and one of the other conductors, suchas conductor 8, which may be provided specifically for this purpose. Forexample, in Figs. 1 and 5 I have illustrated a directly heated getteringmaterial which may comprise barium or barium-strontium strip or ribbon50 supported on a nickel base and connected directly between conductors8 and 9.

Advantages of the type of construction for an electric discharge devicewhich I provide may be more readily appreciated by referring to Fig. 7wherein the method of threading the electrode assembly over theconductors is shown at that stage in the construction where th verticalconductors have just been threaded through the lower Vertical spacer 24.The ease of assembly is believed obvious and the facility with which theconnections between the conductors 1-43, inelusive, and control elementsof the discharge device may be made is believed equally apparent.

The type of construction described above lends itself with equalfacility to discharge devices of the pure electron type or to the arcdischarge type employing an ionizable medium such as a gas or a vapor.For example in the construction of the latter type device, I have foundthat the 'ionizable medium may be any suitable inert gas such 'as argonor xenon.

Figs. 8-11,inclusive, represent a modification of my'invention asapplied to a pentode con struction. Fig. dis 'a partially cut-away viewof an electrode assembly comprising a pair of vertically displacedparallel conducting spacers 5| and 52 provided with a plurality ofopenings 53 and 54 adapted to receive vertical conductors (not shown)similar in arrangement and construction to the conductors shown in Figs.2

and '7. In this modification of my invention, the insulating spacers 5|and 52 may be supported in. the'position illustrated principally bymeans of. a wall-like or plate-like electrode comprising parts orsections 55 and 56 which may constitute the anodeof the discharge.device. The details of the anode construction are shown in Fig. 9.

Sections .55 and 56 of the anode construction may each include pliablemetallic pendants or tabs 51 and 58 which extend through openings in thetop and bottom spacers 5| and 52 and may be turned over to secure thespacers and the anode sections rigidly together as shown in Fig. 8.Anode sections 55 and 56 are provided with arms 59, 63 and 6|,. 62 whichserve as connecting means between the anodesections and one of thevertical conductors which extends through the lower insulating spacer 52so that a connection, or a pair of connections to the anode sections maybe made within the space between the insulating spacers 5| and 52. Itwill be noted that arms 59 and GI and arms 6| and 62 are positioned tocooperate and are provided with substantially semi-cylindricaldeformations to facilitate engagement with a cylindrical verticalconductor. The arms may be welded or soldered to the connecting verticalconductor.

Although not limited thereto, the various electrodes of the assembly maybe supported by a plurality of pins arranged in alinement and extendingthrough appropriately alined openings in the top and bottom spacers 5|and 52. For example, a thermionic cathode 63 may be centrallylocatedrelative to the supporting pins, and a control grid 64 may besupported by a pair of pins 65 and 66; a screengrid 61 is supported by apair of pins 68 and 59, and a suppressor grid is supported by a pair ofpins 1| and I2, the details of the grids and the supporting pinconstruction being shown in Fig. 10.

The arrangement of the connections to the control elements of thedischarge device will be better understood by referring to Figs. 9- and10 wherein vertical conductors '|'3'|6 are shown. It will be noted thatconductor 13 is connected to control grid 54, particularly pin 65, bymeans of a conductor or metallic strap 11 which lies relatively close tothe upper surfaces of insulating spacer 5|. Cathode 63 is connected toconductor 14 by means of a metallic strap 18, and is spaced at arelatively greater distance above. the surface of the insulating spacer5|. In like manner, screen grid 61 is connected toconductor 15 by astrap 19 at a, substantial distance above the top surface of spacer 5|.

- In order to provide electrostatic shielding between the anode pendants51 and 58 which extend above the surface of the insulating spacer 5|, Iprovide a metallic shield 85 which may have a substantial U-shapedconfiguration and which may be connected at the closed end thereof. to

the shield grid pin l2. For example, the pin 12 may be welded to themetallic shield 85 and be positioned between the control element pinsand the pendants 5] and 58, thereby completely shielding the-controlelements including the control grid and the. screen grid'fromanyelectrol6 and the shield 8|] to minimize the length of the conductor andto obviate crossover of the conductor connecting means.

I The above type of construction is readily applicable to rectify andtriode types electric'discharge devices. In discharge devices of thetetrode and pentode types and other types requiring shielding betweencertain of the control elements, the above described construction isassembled in accordance with the above described procedure by separatingthe conductors or lead-in wires to be shielded by suitable interspacedor grounded shielding means such as the shield 3i].

As an additional feature, in order to protect or shield the verticalconductor 13 connected to control grid 54 from the electrostatic effectsof the anode parts 55 and 55, I provide an optimum spacing andpositioning of the grounded vertical conductors. For example, inasmuchas the cathode vertical conductor ?4 is grounded, it may be positionedrelative to anode part 55 and the grid vertical conductor 13 to shieldthe latter therefrom as illustrated in Fig. 8. In like manner, I providean additional grounded vertical conductor 82, shown in Figs. 8 and 11,which may extend through the upper insulating spacer 5| and be turnedover and positioned opposite the end of anode part 56, thereby shieldingthe grid vertical conductor 13 from the latter. This interspacing of thegrounded vertical conductors 14 and 82 to shield the conductor 73electrostatically from the anode parts within the region defined byspacers 5| and 52 is particularly important in those electric dischargedevices where the enclosing envelope is metal in an arrangement such asthat shown in Fig. 1 where a metallic envelope l'completelysurrounds theelectrode assembly and electrodes.

If a relatively short or low-inductance connection to an electrode isdesired, a tab may be connected to the lower end of the electrodeassembly and brought out to the lead-in conductor in a position near theheader, either as the only connection or in conjunction with theconnection at the top of the unit assembly.

While I have shown and described my invention as applied to particulardevices diagrammatically shown, it will be obvious to those skilled inthe art that changes and modifications may be made without departingfrom my invention,

and I, therefore, aim in the appended claims to cover all suchchangesand modifications as fall wall-like electrode for maintaining saidspacers in position and having a plurality of metallic tabs extendingthrough and bent over said spacers to form a rigid assembly, andconductor means positioned above the top insulating spacer forconnecting electrodes to. said vertical conductors.

2, An electric discharge device comprising a metallic header havingsealed thereto a plurality of upright conductors, and an electrodeassembly comprising a plurality o electrodes and a pair of insulatingspacers provided with a plurality of openings through which said uprightconductors are threaded and comprising a screen grid constituting aclosed metallic wall having tabs for maintaining said spacers inposition, and means for connecting said upright conductors to saidelectrodes above the top spacer.

3. An electric discharge device comprising a plurality of enclosedelectrodes and including a metallic header having a plurality of spacedver tical conductors sealed to said header, an electrode assemblycomprising a plurality of electrodes and a pair of horizontal insulatingspacers provided with a plurality of openings through which saidconductors are threaded, one of said electrodes being of wall-likeconstruction provided with a plurality of pendants which are threadedthrough the top and bottom spacers and bent over to secure said spacersto said one electrode, and conductor means above the top insulatingspacer for connecting said electrodes to said conductors.

4. An electric discharge device comprising a plurality of enclosedelectrodes and including a metallic header having a plurality of uprightconductors sealed to said header, a unitary electrode assemblycomprising a pair of verticallydisplaced parallel spacers provided withopenings through which said conductors are threaded, awall-like metallicelectrode between said spacers and having a plurality of metallicpendants adapted for extending through and maintaining said spacers inposition thereagainst, a plurality of conductors positioned above thetop spacer for connecting said electrodes to said conductors, and anenvelope surrounding said conductors and said assembly and sealed tosaid header.

5. An electric discharge device comprising a ietallic header supportinga plurality of spaced vertical conductors, a unitary electrode assemblycomprising a pair of parallel insulating spacers provided with openingsthrough which said conductors are threaded, said electrode assemblycomprising a wall-like metallic grid structure for maintaining saidspacers in position and having a plurality of tabs which are insertedthrough said spacers and bent over to form a rigid assembly, andconductor means for connecting the L ectrodes to said verticalconductors above the top horizontal spacer.

6. An electric discharge device comprising a metallic header supportinga plurality of spaced upright conductors, an electrode assemblycomprising a pair of parallel insulating spacers provided with openingsthrough which said conductors are threaded, a screen grid structurecomprising a closed metallic wall provided with tabs for engaging saidspacers and for maintaining said spacers and said screen grid structurein juxtaposition, and conductor means for connecting the electrodes ofsaid device to said upright conductors above the top horizontal spacer.

7. An electric discharge device comprising a plurality of enclosedelectrodes and a metallic header provided with a plurality of spacedvertical conductors sealed to said header, a cathode and control memberassembly including a pair of vertically-spaced parallel insulatingspacers provided with openings through which said conductors arethreaded, said cathode and said control members being supported by saidspacers and one of said electrodes being of a wall-like configurationprovided with metallic pendants adapted to extend through and be bentover to maintain said spacers against said one electrode, a metallicplate attached to one of said conductors and constituting an anodewithin the enclosure provided by said one electrode, and conductorspositioned above the top insulating spacer for connecting said cathodeand said control members to the first mentioned conductors.

8. An electric discharge device comprising a metallic header supportinga plurality of spaced vertical conductors which are sealed to saidheader, a unitary electrode assembly comprising a pair of parallelinsulating spacers provided with openings through which said conductorsare. threaded, a plurality of electrodes comprising a screen grid havinga wall-like metallic structure for maintaining said spacers in positionand having a lurality of metallic tabs which extend through said spacersand are bent over to secure said spacers. to said one electrode, saidinsulating spacers serving as a support for other spaced electrodes, andconductor means positioned above the top insulating spacer forconnecting the electrodes to said vertical conductors.

9. An electric discharge device comprising a metallic header supportinga plurality of spaced vertical conductors which are sealed to saidheader, a unitary electrode assembly comprising a pair of parallelinsulating spacers provided with openings through which said conductorsare threaded, a plurality of electrodes one of which comprises awall-like metallic structure for maintaining said spacers in positionand having. a plurality of pendants threaded through said spacers andturned over to secure said spacers and said one electrode firmly inposition, said spacers serving to support in vertical position otherelectrodes, and conductor means positioned above the top insulatingspacer for connecting the electrodes to said vertical conductors.

10. An electric discharge device comprising a header supporting aplurality of spaced vertical conductors, an electrode assemblycomprising a pair of parallel insulating spacers provided with openingsthrough which said conductors are threaded, one of said conductors beingprovided with a substantial surface to constitute an anode, saidelectrode assembly comprising a wall-like electrode for securing andmaintaining said spacers in position to form a rigid construction, andconductor means positioned above the top insulating spacer forconnecting the electrodes to said vertical conductors.

11. An electric discharge device comprising a header supporting aplurality of spaced Vertical conductors, an electrode assemblycomprising a pair of parallel insulating spacers provided with openingsthrough which said conductors are threaded, said electrode assemblycomprising a substantial wall-like anode construction which anodeconstruction includes means for maintaining said spacers in position,the electrodes being supported by said spacers including a cathode and acontrol element, and conductor means positioned above the top insulatingspacer for connecting said cathode and said control element topredetermined different vertical conductors.

12. An electric discharge device comprising a' header supporting aplurality of spaced vertical conductors, an electrode assemblycomprising a pair of parallel insulating spacers provided with openingsto which said conductors are threaded, said electrode assemblycomprising a wall-like anode construction including means formaintaining said spacers in position, the electrodes supported by saidspacers including a cathode and a control element, said anode beingconnected to one of said vertical conductors at a point intermediatesaid spacers, and conductor means positioned above the top insulatingspacer for connecting said cathode and said control element to difierentvertical conductors.

13. An electric discharge device comprising a metallic header supportinga plurality of spaced vertical conductors sealed to said header, aunitary electrode assembly comprising a plurality of horizontalinsulating spacers provided with openings through which said conductorsare threaded, said electrode assembly comprising a wall-like metallicstructure for maintaining said spacers in position and having aplurality of metallic pendants which extend through said spacers andmaintain said structure and said spacers in position, a cathodemaintained in a vertical position by said horizontal spacers byextending through openings therein, a control electrode supported in avertical position by said horizontal spacers, an anode constituting aplate member attached to one of said vertical conductors and positionedwithin said wall-like structure, and conductor means positioned abovethe top insulating spacer for connecting said cathode, said controlelectrode and said wall-like structure individually to predetermineddifferent vertical conductors.

14. An electric discharge device comprising a metallic header supportinga plurality of spaced vertical conductors, an electrode assemblycomprising a pair of parallel insulating spacers provided with openingsthrough which said conductors are threaded, said electrode assemblycomprising a wall-like anode construction including means formaintaining said spacers in position, the electrodes supported by saidspacers including a cathode and a plurality of control elements, saidanode being connected to one of the Vertical conductors at a pointintermediate said spacers, conductor means for connecting said controlelements supported by said spacers to different predetermined verticalconductors, and shielding means above the top spacer for shielding saidconductor means and the supported electrodes.

15. An electric discharge device comprising a plurality of enclosedelectrodes and including a metallic header having a plurality of spacedvertical conductors sealed to said header, an electrode assemblycomprising a pair of horizontal insulating spacers provided with aplurality of openings through which said conductors are individuallythreaded, said electrodes comprising a cathode, an electrostatic controlelement and an anode constituting two opposed plate-surfaces, saidplate-surfaces being provided with a plurality of bent-over metallicpendants extending through said surfaces to maintain said plate membersand said surfaces in position, said plate-surfaces being connected toone of the first mentioned conductors within the region between saidspacers, conductor means positioned above the top spacer 101' connectingsaid cathode and said control element to predetermined conductors of thefirstmentioned conductors, and'electrostatic shielding means positionedbetween said anode and said control element and associated connectingconductor.

16.An electric discharge device comprising a metallic header supportinga plurality of spaced upright conductors, an electrode assemblycomprising ,a pair of horizontal insulating spacers provided withopenings through which said conductors are threaded, said electrodescomprising an anode, a cathode and acontrol element, said anodecomprising a wall-like member having metallic pendants adapted toextend, through said spacers to maintain said spacers in juxtapositionto said anode, conductor means positioned above the top insulatingspacer for connecting said cathode and said control element topredetermined conductors of said plurality of conductors, and shieldingmeans positioned near the top of said anode and lying between saidpendants and the conductor connected to said control element forelectrostatically shielding said control element and associatedconductor.

17. An electric discharge device comprising a header supporting aplurality of spaced vertical conductors, and an electrode assemblycomprising a pair of parallel insulating spacers provided with openingsthrough which said conductors are threaded, said electrode assemblycomprising an anode comprising two opposing members and at least onecontrol element in spaced relation with said members and a pair ofgrounded metal conductors interposed between the anode members and thevertical conductor connected to said control element.

18. An electric discharge device comprising a metallic header havingsealed thereto a plurality of upright conductors, and a unitaryelectrode assembly comprising a pair of parallel insulating spacersprovided with openings through which said conductors are threaded, saidelectrode assembly comprising a cathode and a pair of oppositelydisposed anode members for maintaining said spacers in position and acontrol element positioned between said pair of anode members, and ametallic envelope enclosing said electrode assembly, said conductorsbeing arranged so that grounded conductors are interposed between saidanode members and the grid conductor thereby shielding said gridconductor electrostatically from said anode members Within the regionintermediate said spacers.

19. An electric discharge device comprising a metallic header supportinga plurality of spaced vertical conductors, a unitary electrode assemblycomprising a plurality of parallel insulating spacers provided withopenings through which said conductors are threaded, said electrodeassembly comprising an anode including two opposing plate-like membersfor maintaining said spacers in position, a cathode and a controlelement intermediatesaid plate-like members, and a metallic envelopeenclosing said electrode assembly and sealed to said header, saidvertical conductors being arranged so that grounded vertical conductorsare positioned opposite the ends of said plate-like members andinterposed between said plate-like members and the grid verticalconductor thereby shielding the latter from the anode constructionwithin the region intermediate said spacers.

JAMES E. BEGGS.

